Auto-mount defpages: eliminate Python route stubs across all 9 services

Defpages are now declared with absolute paths in .sx files and auto-mounted
directly on the Quart app, removing ~850 lines of blueprint mount_pages calls,
before_request hooks, and g.* wrapper boilerplate. A new page = one defpage
declaration, nothing else.

Infrastructure:
- async_eval awaits coroutine results from callable dispatch
- auto_mount_pages() mounts all registered defpages on the app
- g._defpage_ctx pattern passes helper data to layout context

Migrated: sx, account, orders, federation, cart, market, events, blog

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

blog/bp/blog/routes.py

@@ -53,16 +53,6 @@ def register(url_prefix, title):
     @blogs_bp.before_request
     async def route():
       g.makeqs_factory = makeqs_factory
-      ep = request.endpoint or ""
-      if "defpage_new_post" in ep:
-          from sx.sx_components import render_editor_panel
-          g.editor_content = render_editor_panel()
-      elif "defpage_new_page" in ep:
-          from sx.sx_components import render_editor_panel
-          g.editor_page_content = render_editor_panel(is_page=True)
-
-    from shared.sx.pages import mount_pages
-    mount_pages(blogs_bp, "blog", names=["new-post", "new-page"])
 
     @blogs_bp.context_processor
     async def inject_root():
@@ -277,7 +267,7 @@ def register(url_prefix, title):
       await invalidate_tag_cache("blog")
 
       # Redirect to the edit page
-      return redirect(host_url(url_for("blog.post.admin.defpage_post_edit", slug=post.slug)))
+      return redirect(host_url(url_for("defpage_post_edit", slug=post.slug)))
 
 
     @blogs_bp.post("/new-page/")
@@ -335,7 +325,7 @@ def register(url_prefix, title):
       await invalidate_tag_cache("blog")
 
       # Redirect to the page admin
-      return redirect(host_url(url_for("blog.post.admin.defpage_post_edit", slug=page.slug)))
+      return redirect(host_url(url_for("defpage_post_edit", slug=page.slug)))
 
 
     @blogs_bp.get("/drafts/")